When deciding to treat a patient with the help of a catheter, the benefit of the treatment always has to be balanced against the risk of nosocomial infections, since there is always a risk that bacteria or other microorganisms spread by touch or air contamination grow in the catheter. In order to reduce the risk of infections, a lock solution is applied in the catheter when it has been disconnected from e.g. a dialysis machine or due to therapeutic interventions such as application of contrast media or instillation of fluids or medication. The lock solution provides a kind of liquid barrier for growth of bacteria and other microorganisms. It may contain e.g. heparin, citrate or taurolidine.
In order to further reduce the risk of infections and to simplify the application of the'lock solution, pre-filled syringes with lock solution may be used.
Pre-filled syringes are known containing saline solution for rinsing or e.g. a heparin solution for use as lock solution. Such syringes are marketed e.g. by BD under the name BD PosiFlush™. These syringes are provided with a so-called luer lock for connecting the syringe to the catheter. Although the solutions in the pre-filled syringe are sterile a problem with maintaining sterility remains, since microorganisms may be introduced by touch or air contamination at the opening of the catheter when connecting and disconnecting the syringe.